Delayed sensorineural deafness and skin carcinogenesis in a Japanese xeroderma pigmentosum group D patient

A 65-year-old patient with xeroderma pigmentosum (XP), XP77TO, was assigned to complementation Group D by the cell-fusion study and comprised the fifth Group D case in Japan. The patient had mild solar sensitivity by age 7, dyspigmentation by 10 years, and he still currently has moderate symptoms. The skin phototest by 290, 300 and 305 nm monochromatic ultraviolet (UV) light revealed a delayed peak of erythema 48 h post-irradiation and lowered minimal erythemal doses. The XP77TO skin fibroblasts, as well as a reference Group D strain, exhibited the same 7-fold higher sensitivity to the lethal effect of 254 nm UV as did normal cells. Unscheduled DNA synthesis (UDS) induced in XP77TO cells by 254 nm UV (10 J/m2) was 42% of normal, falling into the Group D range of 25-50% UDS. In spite of such a similar cellular phenotype, XP77TO developed squamous cell carcinomas at 44 and 65 years of age and audiometric sensorineural deafness in a delayed fashion at advanced age.